Axle driving apparatus for a zero turn radius vehicle

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an axle driving apparatus designed to drive a zero turn radius vehicle.

Background Art

An axle driving apparatus having a hydrostatic transmission (HSTs) is generally known in the art. An HST includes a center section on which is mounted a hydraulic pump and a hydraulic motor. The hydraulic pump and the hydraulic motor each carry a plurality of reciprocating pistons that are in fluid communication through porting formed in the center section. As the hydraulic pump rotates, the pump pistons move axially as they bear against an adjustable swash plate where the degree of axial movement depends upon the angular orientation of the swash plate. Axial movement of the pump pistons forces the hydraulic fluid through the porting, which forces the motor pistons against a thrust bearing to thereby rotate the hydraulic motor. As the hydraulic motor rotates, hydraulic fluid is returned to the hydraulic pump through the porting. In this manner, the rotation of the hydraulic pump is translated to the hydraulic motor and the rotation of the hydraulic motor may be used to drive an axle or a pair of axles through a differential. In the case of a transaxle, both left and right wheels are driven together so the speed cannot be independently controlled. This results in a larger turning radius, making it difficult to make close turns. When used in lawn or garden tractors, it is difficult to move close to trees or other obstacles.

Alternatively, there can be one HST for each wheel so that each wheel can be driven independently. Such zero turn HSTs provide for independent control of each of the drive wheels. Improvements and modifications are frequently being made to HSTs with a zero turn radius.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein is an axle driving apparatus of a first embodiment that includes a first housing having a first plurality of cooling fins; a first axle, having a first longitudinal axis, rotatably mounted in the first housing; a first hydraulic stepless speed change assembly disposed within the first housing, the first hydraulic stepless speed change assembly including a first hydraulic pump having a first input shaft, said first input shaft having a rotational axis substantially perpendicular to said first axle, and including a first hydraulic motor having a first output shaft drivingly connected to said first axle; a second housing having a second plurality of cooling fins; a second axle, having a second longitudinal axis, rotatably mounted in the second housing; a second hydraulic stepless speed change assembly disposed within the second housing, the second hydraulic stepless speed change assembly including a second hydraulic pump having a second input shaft, said second input shaft having a rotational axis substantially perpendicular to said second axle, and including a second hydraulic motor having a second output shaft drivingly connected to said second axle; and a connecting means connecting the first and second housings. The first plurality of cooling fins and the second plurality of cooling fins have different configurations.

Further, the first plurality of cooling fins may be bent at an angle different from an angle at which the second plurality of cooling fins are bent.

The axle driving apparatus may also include a first hydraulic PTO unit having a first charge pump, wherein the first hydraulic PTO unit is connected to a first plurality of auxiliary ports in the first housing.

Further, the second housing may have a second plurality of auxiliary ports.

The axle driving apparatus may also include a second hydraulic PTO unit having a second charge pump, wherein the second hydraulic PTO unit is connected to the second plurality of auxiliary ports.

Further, the second plurality of auxiliary ports may be closed off.

The axle driving apparatus may also include a first input pulley disposed on the first input shaft and a second input pulley disposed on the second input shaft.

The axle driving apparatus may also include a first spline collar surrounding the first input shaft; a first bearing support surrounding the first spline collar; a second spline collar surrounding the second input shaft; and a second bearing support surrounding the second spline collar. The first input pulley may be disposed on the first bearing support and the second input pulley may be disposed on the second bearing support.

The axle driving apparatus may also include a first input pulley; a first cooling fan mounted on the first input shaft; a first wave washer located between the first input pulley and the first cooling fan; a second input pulley; a second cooling fan mounted on the second input shaft; and a second wave washer located between the second input pulley and the second cooling fan.

The axle driving apparatus may also include a first oil sump formed in the first housing, wherein the first hydraulic stepless speed change assembly is at least partially immersed in the first oil sump; a first reserve tank; a first siphon allowing flow in both directions between the first oil sump and the first reserve tank; a second oil sump formed in the second housing, wherein the second hydraulic stepless speed change assembly is at least partially immersed in the second oil sump; a second reserve tank; and a second siphon allowing flow in both directions between the second oil sump and the second reserve tank.

The axle driving apparatus may also include a first detachable oil filter associated with the first housing and a second detachable oil filter associated with the second housing.

The axle driving apparatus may also include a first removable lid for accessing the first detachable oil filter and a second removable lid for accessing the second detachable oil filter.

Further, the first detachable oil filter may be positioned on a bottom surface of a first housing and the second detachable oil filter may be positioned on a bottom surface of a second housing.

Alternatively, the first detachable oil filter may be positioned on a rear side of a first housing and the second detachable oil filter may be positioned on a rear side of a second housing.

Further, the first hydraulic pump may be mounted within the first housing a first preselected distance from the first axle and the first hydraulic motor may be mounted within the first housing a second preselected distance from the first axle, the second preselected distance being greater than the first preselected distance. In addition, the second hydraulic pump may be mounted within the second housing a third preselected distance from the second axle and the second hydraulic motor may be mounted within the second housing a fourth preselected distance from the second axle, the fourth preselected distance being greater than the third preselected distance.

The axle driving apparatus may also include a first rotary bypass valve assembly disposed in the first housing, the first rotary bypass valve assembly including a first rotary shaft having a first end extending from the housing and at least two oil holes and including a first bypass arm connected to the first end of the first rotary shaft for rotating the first rotary shaft to connect and disconnect the at least two oil holes with oil drain ports connected to the first hydraulic motor. The axle driving apparatus may also include a second rotary bypass valve assembly disposed in the second housing, the second rotary bypass valve assembly including a second rotary shaft having a first end extending from the second housing and at least two oil holes and including a second bypass arm connected to the first end of the second rotary shaft for rotating the second rotary shaft to connect and disconnect the at least two oil holes with oil drain ports connected to the second hydraulic motor.

Further, the first hydraulic stepless speed change assembly may include a first counter shaft with a first braking mechanism and the second hydraulic stepless speed change assembly may include a second counter shaft with a second braking mechanism.

Further still, the first hydraulic stepless speed change assembly may further include a third counter shaft and the second hydraulic stepless speed change assembly may further include a fourth counter shaft.

The axle driving apparatus may also include a first magnet located in the first housing; a second magnet located in the first housing; a third magnet located in the first housing; a fourth magnet located in the second housing; a fifth magnet located in the second housing; and a sixth magnet located in the second housing.

Further, the first housing may have a first chamber, a second chamber and an opening between the first chamber and the second chamber; the first magnet is located in the first chamber; the second magnet is located in the second chamber; and the third magnet is located in the opening between the first chamber and the second chamber. In addition, the second housing may have a third chamber, a fourth chamber and an opening between the third chamber and the fourth chamber; the fourth magnet is located in the third chamber; the fifth magnet is located in the fourth chamber; and the sixth magnet is located in the opening between the third chamber and the fourth chamber.

The axle driving apparatus may also include a first check valve located in the first speed change assembly; a second check valve located in the first speed change assembly; a third check valve located in the first speed change assembly; a fourth check valve located in the second speed change assembly; a fifth check valve located in the second speed change assembly; and a sixth check valve located in the second speed change assembly.

Further, the first check valve may be located in a first oil passage in the first hydraulic pump, the second check valve may be located in a second oil passage in the first hydraulic pump, the fourth check valve may be located in a third oil passage in the second hydraulic pump, and the fifth check valve may be located in a fourth oil passage in the second hydraulic pump.

Further still, the axle driving apparatus may include a first charge pump with a first oil groove, wherein the third check valve is located in the first oil groove and a second charge pump with a second oil groove, wherein the sixth check valve is located in the second oil groove.

Further, the connecting means may be a bar and/or a plate.

Also disclosed herein is an axle driving apparatus of a second embodiment that includes a housing; a single axle, having a longitudinal axis, rotatably mounted in the housing; and a hydraulic stepless speed change assembly disposed within the housing, the speed change assembly including a hydraulic pump having an input shaft projecting from the housing, the input shaft having a rotational axis substantially perpendicular to the single axle, and including a hydraulic motor having an output shaft drivingly connected to the single axle. The hydraulic pump is mounted within the housing a first preselected distance from the single axle and the hydraulic motor is mounted within the housing a second preselected distance from the single axle, the second preselected distance being greater than the first preselected distance.

Also disclosed herein is an axle driving apparatus of a third embodiment that includes a housing; a single axle, having a longitudinal axis, rotatably mounted in the housing; a hydraulic stepless speed change assembly disposed within the housing, the speed change assembly including a hydraulic pump having an input shaft projecting from the housing, the input shaft having a rotational axis substantially perpendicular to the single axis, and including a hydraulic motor having an output shaft drivingly connected to the single axle; and a rotary bypass valve assembly disposed in the housing. The rotary bypass valve assembly includes a rotary shaft having a first end extending from the housing and at least two oil holes and includes a bypass arm connected to the first end of the rotary shaft for rotating the rotary shaft to connect and disconnect the at least two oil holes with oil drain ports connected to the hydraulic motor.

Also disclosed herein is an axle driving apparatus of a fourth embodiment that includes a housing; a single axle, having a longitudinal axis, rotatably mounted in the housing; and a hydraulic stepless speed change assembly disposed within the housing. The speed change assembly includes a hydraulic pump having an input shaft projecting from the housing, the input shaft having a rotational axis substantially perpendicular to the single axis; a hydraulic motor having an output shaft drivingly connected to the single axle; and a first counter shaft with a braking mechanism.

Further, the hydraulic stepless speed change assembly may include a second counter shaft.

Further, the braking mechanism may include a fixed friction pad; a movable friction pad having a cam projection; a brake rotor surrounding a gear attached to the first counter shaft and located between the fixed friction pad and the movable friction pad; a rotary brake shaft having a first end having a groove and engaged with the movable friction pad; and a brake arm connected to a second end of a rotary brake shaft for rotating the rotary brake shaft to move the movable friction pad closer to the fixed friction pad and press the brake rotor therebetween.

Also disclosed herein is an axle driving apparatus of a fifth embodiment that includes a housing; a single axle, having a longitudinal axis, rotatably mounted in the housing; a hydraulic stepless speed change assembly disposed within the housing, the speed change assembly including a hydraulic pump having an input shaft projecting from the housing, the input shaft having a rotational axis substantially perpendicular to the single axis, and including a hydraulic motor having an output shaft drivingly connected to the single axle; a first magnet; a second magnet; and a third magnet.

Further, the housing may have a first chamber, a second chamber and an opening between the first chamber and the second chamber; the first magnet located may be in the first chamber; the second magnet may be located in the second chamber; and the third magnet may be located in the opening between the first chamber and the second chamber.

Also disclosed herein is an axle driving apparatus of a sixth embodiment that includes a housing; a single axle, having a longitudinal axis, rotatably mounted in the housing; a hydraulic stepless speed change assembly disposed within the housing, the speed change assembly including a hydraulic pump having an input shaft projecting from the housing, the input shaft having a rotational axis substantially perpendicular to the single axis, and including a hydraulic motor having an output shaft drivingly connected to the single axle; a first check valve; a second check valve; and a third check valve.

Further, the first check valve may be located in a first oil passage in the hydraulic pump and the second check valve may be located in a second oil passage in the hydraulic pump.

Still further, the axle driving apparatus may include a charge pump with an oil groove, wherein the third check valve may be located in the oil groove.

Also disclosed herein is an axle driving apparatus of a seventh embodiment that includes a housing; a single axle, having a longitudinal axis, rotatably mounted in the housing; a hydraulic stepless speed change assembly disposed within the housing, the speed change assembly including a hydraulic pump having an input shaft projecting from the housing, the input shaft having a rotational axis substantially perpendicular to the single axis, and including a hydraulic motor having an output shaft drivingly connected to the single axle; and an input pulley disposed on the input shaft.

Further, the axle driving apparatus may include a spline collar surrounding the input shaft and a bearing support surrounding the spline collar, wherein the input pulley is disposed on the bearing support.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The above mentioned features of the invention will be more clearly understood from the following detailed description of the invention read together with the drawings in which:

<figref idrefs="DRAWINGS">FIG. 1</figref> illustrates a side view, partly in cross-section, of an exemplary working vehicle, such vehicle being an example of one type of vehicle on which an axle driving apparatus disclosed herein can be utilized.

<figref idrefs="DRAWINGS">FIG. 2</figref> illustrates a front view of the vehicle.

<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates a plan view of the vehicle showing the transaxle assembly.

<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates a first embodiment of a hydraulic circuit diagram for a transaxle assembly.

<figref idrefs="DRAWINGS">FIG. 5</figref> illustrates a plan view, partially in cross-section, of a left transaxle.

<figref idrefs="DRAWINGS">FIG. 6</figref> illustrates a cross-sectional view taken along line VI-VI in <figref idrefs="DRAWINGS">FIG. 5</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 7</figref> illustrates a cross-sectional view taken along line VII-VII in <figref idrefs="DRAWINGS">FIG. 5</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 8</figref> illustrates a cross-sectional view taken along line VIII-VIII in <figref idrefs="DRAWINGS">FIG. 5</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 9</figref> illustrates a cross-sectional view taken along line IX-IX in <figref idrefs="DRAWINGS">FIG. 5</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 10</figref> illustrates a cross-sectional view taken along line X-X in <figref idrefs="DRAWINGS">FIG. 5</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 11</figref> illustrates a cross-sectional view taken along line XI-XI in <figref idrefs="DRAWINGS">FIG. 6</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 12</figref> illustrates a cross-sectional view taken along line XII-XII in <figref idrefs="DRAWINGS">FIG. 6</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 13</figref> illustrates a cross-sectional view taken along line XIII-XIII in <figref idrefs="DRAWINGS">FIG. 5</figref> of the left transaxle.

<figref idrefs="DRAWINGS">FIG. 14</figref> illustrates a top view of the center section.

<figref idrefs="DRAWINGS">FIG. 15</figref> illustrates a bottom view of the center section.

<figref idrefs="DRAWINGS">FIG. 16</figref> illustrates a left side view of the center section in partial cross-section.

<figref idrefs="DRAWINGS">FIG. 17</figref> illustrates a cross-sectional view taken along line XVII-XVII in <figref idrefs="DRAWINGS">FIG. 14</figref> of the center section.

<figref idrefs="DRAWINGS">FIG. 18</figref> illustrates a cross-sectional view taken along line XVIII-XVIII in <figref idrefs="DRAWINGS">FIG. 16</figref> of the center section.

<figref idrefs="DRAWINGS">FIG. 19</figref> illustrates a cross-sectional view taken along line XIX-XIX in <figref idrefs="DRAWINGS">FIG. 16</figref> of the center section.

<figref idrefs="DRAWINGS">FIG. 20</figref> illustrates a cross-sectional view taken along line XX-XX in <figref idrefs="DRAWINGS">FIG. 14</figref> of the center section.

<figref idrefs="DRAWINGS">FIG. 21</figref> illustrates a front view of a speed control arm and a bypass arm.

<figref idrefs="DRAWINGS">FIG. 22</figref> illustrates a cross-sectional view taken along line XXII-XXII in <figref idrefs="DRAWINGS">FIG. 21</figref> of the speed control arm and the bypass arm.

<figref idrefs="DRAWINGS">FIG. 23</figref> illustrates a cross-sectional view taken along line XXIII-XXIII in <figref idrefs="DRAWINGS">FIG. 22</figref> of the speed control arm and the bypass arm.

<figref idrefs="DRAWINGS">FIG. 24</figref> illustrates a side view of a first embodiment of a pulley and cooling fan attached to a pump shaft.

<figref idrefs="DRAWINGS">FIG. 25</figref> illustrates a side view of a second embodiment of a pulley and cooling fan attached to a pump shaft.

<figref idrefs="DRAWINGS">FIG. 26</figref> illustrates a second embodiment of a hydraulic circuit diagram for a transaxle assembly.

<figref idrefs="DRAWINGS">FIG. 27</figref> illustrates a third embodiment of a hydraulic circuit diagram for a transaxle assembly, with a right transaxle and a left transaxle having a different hydraulic circuit.

<figref idrefs="DRAWINGS">FIG. 28</figref> illustrates a cross-sectional view of a transaxle illustrating a common housing material and a filter removable from a lower housing part.

DETAILED DESCRIPTION OF THE INVENTION

The axle driving apparatus disclosed herein is designed to drive a vehicle. An exemplary vehicle is shown generally at <b>1</b> in <figref idrefs="DRAWINGS">FIGS. 1-6</figref>. Vehicle <b>1</b> is a zero turn radius (ZTR) riding lawn mower. Vehicle <b>1</b> includes a body frame <b>3</b> movably supported by oppositely disposed drive wheels <b>10</b>L and <b>10</b>R. A pair of caster wheels <b>19</b>L and <b>19</b>R are secured to a forward portion of body frame <b>3</b>. Vehicle <b>1</b> also has an operator's seat <b>16</b>, driving and steering control handles <b>17</b>L and <b>17</b>R, and a brake pedal <b>18</b>.

Drive wheels <b>10</b>L and <b>10</b>R are rotatably driven by a prime mover, such as engine <b>2</b>, mounted on body frame <b>3</b>. Drive wheels <b>10</b>L and <b>10</b>R are carried on left and right axle shafts <b>9</b>L and <b>9</b>R, respectively, each of which have a wheel mounting flange <b>9</b><i>a</i>. Axle shafts <b>9</b>L and <b>9</b>R extend from left and right transaxles <b>8</b>L and <b>8</b>R, respectively, each of which have a housing <b>20</b>. Each housing <b>20</b>, has an upper housing part <b>21</b> with frame mounting bosses <b>22</b> extending therefrom to attach transaxles <b>8</b>L and <b>8</b>R to a mounting stay <b>3</b><i>a</i>, which extends downward from body frame <b>3</b>. A single axle shaft <b>9</b>L(<b>9</b>R) is placed in each housing <b>20</b> defining a longitudinal axis and having a proximal end rotatably mounted in housing <b>20</b> and a distal end extending outwardly from a outside wall of housing <b>20</b>. Each housing <b>20</b>, also has axle support projections <b>33</b>U and <b>33</b>L, as shown in <figref idrefs="DRAWINGS">FIG. 7</figref>, which help to maintain the location of proximal end of axle shaft <b>9</b>L(<b>9</b>R). The distal end of axle shaft <b>9</b>L(<b>9</b>R) extends through a tubular portion formed in upper housing part <b>21</b> and is supported by a bearing fitted inside said upper housing <b>21</b>, then extends outward from housing <b>20</b>.

A shaft <b>2</b><i>a </i>extends downward from engine <b>2</b> to drive an output pulley <b>4</b>, a PTO (power take-off) electric clutch <b>12</b>, and an output pulley <b>11</b>. A belt <b>5</b> fits around output pulley <b>4</b> and input pulleys <b>6</b>L and <b>6</b>R, which are located on transaxles <b>8</b>L and <b>8</b>R, below cooling fans <b>7</b>L and <b>7</b>R, respectively. A belt <b>13</b> fits around output pulley <b>13</b> and an input pulley <b>14</b> that is connected to a shaft <b>15</b><i>a </i>extending from a mower <b>15</b> positioned beneath body frame <b>3</b>.

<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates a plan view of a transaxle assembly including transaxles <b>8</b>L and <b>8</b>R. Housings <b>20</b> of transaxles <b>8</b>L and <b>8</b>R are separate and distinct from one another and do not have a shared common housing. Facing side surfaces of upper housing parts <b>21</b> of transaxles <b>8</b>L and <b>8</b>R are connected together with a connecting bar <b>137</b> that extends from openings <b>24</b>, as shown in <figref idrefs="DRAWINGS">FIG. 10</figref>, in upper housing parts <b>21</b> of transaxles <b>8</b>L and <b>8</b>R to span a space between transaxles <b>8</b>L and <b>8</b>R. Ends of connecting bar <b>137</b> may be pressure fitted or friction fitted into openings <b>24</b>, which are coaxial to axles <b>9</b>L and <b>9</b>R. A pair of hollow tubes <b>138</b> are rotatably mounted on connecting bar <b>137</b> allowing for contact with belt <b>13</b> when mower <b>15</b> is lifted up. In addition, upper surfaces of upper housing parts <b>21</b> of transaxles <b>8</b>L and <b>8</b>R are also connected together via a connecting plate <b>139</b> that is bolted to the upper surfaces of upper housing parts <b>21</b>. Although both are shown, the connecting means between transaxles <b>8</b>L and <b>8</b>R may be connecting bar <b>137</b> alone, connecting plate <b>139</b> alone, or both connecting bar <b>137</b> and connecting plate <b>139</b>. Connecting transaxles <b>8</b>L and <b>8</b>R in this fashion leaves a space therebetween that allows for the passage of belt <b>13</b> in the space between transaxles <b>8</b>L and <b>8</b>R giving the advantage of a greater ground clearance of output pulley <b>11</b>.

As mentioned above, housings <b>20</b> of transaxles <b>8</b>L and <b>8</b>R are separate and distinct from one another. Housings <b>20</b> are not mirror images of one another and have distinguishing features. For example, cooling fins or ribs <b>23</b>L and <b>23</b>R, which extend from an upper surface of upper housing parts <b>21</b>, may have different configurations and/or profiles from one another. For instance, as shown in <figref idrefs="DRAWINGS">FIG. 3</figref> cooling fins or ribs <b>23</b>L may be bent at a different angle than cooling fins or ribs <b>23</b>R. The configuration and profile of cooling fins or ribs <b>23</b>L and <b>23</b>R optimizes and improves air flow for cooling oil within transaxles <b>8</b>L and <b>8</b>R. Cooling fans <b>7</b>L and <b>7</b>R rotate together with input pulleys <b>6</b>L and <b>6</b>R in the same direction. Cooling fins or ribs <b>23</b>L and <b>23</b>R are formed along the direction of cooling air flow for improved cooling efficiency so that the overall profile of right and left transaxles <b>8</b>L and <b>8</b>R are asymmetrical.

Transaxles <b>8</b>L and <b>8</b>R have the same components and while left transaxle <b>8</b>L will be described with reference to <figref idrefs="DRAWINGS">FIGS. 5-26</figref>, right transaxle <b>8</b>R has the same components. Transaxle <b>8</b>L has a housing <b>20</b> that includes an upper housing part <b>21</b> and a lower housing part <b>26</b> joined together with bolts <b>27</b>. Housing <b>20</b> has a hydraulic stepless speed change assembly disposed therein. The hydraulic stepless speed change assembly includes a hydraulic variable displacement axial piston pump <b>50</b> and a hydraulic fixed displacement axial piston motor <b>60</b>. A center section <b>67</b> is mounted in an enlarged region of housing <b>40</b> and has a pump mounting surface <b>70</b> for mounting pump <b>50</b> thereon and has a motor mounting surface <b>73</b> for mounting motor <b>60</b> thereon. Center section <b>67</b> is attached to upper housing part <b>21</b> through a plurality of bolts <b>68</b>, each of which pass through a hollow dowel pin <b>69</b>. Dowel pin <b>69</b> allows for the correct positioning of center section <b>67</b> at a predetermined position. Housing <b>20</b> has a first chamber <b>31</b> housing a gear train, a second chamber <b>34</b> serving as an oil sump, and a third chamber <b>39</b>, as shown in <figref idrefs="DRAWINGS">FIG. 13</figref>.

Pump <b>50</b> is mounted within housing <b>20</b> a first preselected distance from axle <b>9</b>L and motor <b>60</b> is mounted within housing <b>20</b> a second preselected distance from axle <b>9</b>L. The second preselected distance is greater than the firs preselected distance. This may be achieved by having center section <b>67</b> be d-shaped such that pump <b>50</b> is located between axle <b>9</b>L and motor <b>60</b>. The rotational axis of pump <b>50</b> located on center section <b>67</b> is perpendicular to the rotational axis of axle shaft <b>9</b>L and the rotational axis of motor <b>60</b> located on center section <b>67</b> is parallel to the rotational axis of axle shaft <b>9</b>L in the second chamber <b>34</b>. This arrangement brings the pump shaft <b>51</b> close to engine <b>2</b>, thereby decreasing the amount of space need to mount transaxle <b>8</b>L. The arrangement also locates pump shaft <b>51</b> substantially in the middle of the housing <b>20</b> so that cooling fan <b>7</b>L located at an external distal end of pump shaft <b>51</b> can cover substantially the entirety of housing <b>20</b> and thereby efficiently circulate cooling air.

As best seen in <figref idrefs="DRAWINGS">FIG. 5</figref>, one end of motor <b>60</b> is mounted on to motor mounting surface <b>73</b> of center section <b>67</b> via a valve plate <b>63</b> having a pair of openings for communication with kidney ports <b>74</b><i>a </i>and <b>74</b><i>b</i>. Motor <b>60</b> includes a cylinder block <b>62</b> which is rotatably disposed on valve plate <b>63</b>. A plurality of pistons are fitted for reciprocating movement into a plurality of cylinder bores defined in cylinder block <b>62</b>. The other end of motor <b>60</b> has a fixed swash plate <b>64</b>. The heads of the pistons abut a thrust bearing of the fixed swash plate <b>64</b>. A motor output shaft <b>61</b> extends longitudinally through cylinder block <b>62</b> parallel to axle shaft <b>9</b>L. One end of motor shaft <b>61</b> extends through an opening in valve plate <b>63</b> and the other end extends through an opening in fixed swash plate <b>64</b>.

A first counter shaft <b>119</b> extends longitudinally parallel to and adjacent to motor shaft <b>61</b>. A second counter shaft <b>122</b> extends longitudinally parallel to and is located between first counter shaft <b>119</b> and axle shaft <b>9</b>L. An output gear <b>118</b> is provided on motor shaft <b>61</b>, which engages with a first reduction gear <b>120</b> mounted on first counter shaft <b>119</b>, which in turn engages with a second reduction gear <b>123</b> mounted a pinion gear <b>124</b> mounted on second counter shaft <b>122</b>. Second reduction gear <b>123</b> then in turn engages with a bull gear <b>125</b> mounted on axle shaft <b>9</b>L. This gear train transmits the driving force from motor shaft <b>61</b> to axle shaft <b>9</b>L in the first chamber <b>31</b>.

A braking mechanism is shown in FIGS. <b>9</b> and <b>21</b>-<b>23</b>. A brake rotor <b>121</b> engages first reduction gear <b>120</b> mounted on first counter shaft <b>119</b>. Brake rotor <b>121</b> rotates with motor shaft <b>61</b> between a fixed friction pad <b>128</b> and a movable friction pad <b>130</b>. Fixed friction pad <b>128</b> is fitted to upper housing part <b>21</b>. Movable friction pad <b>130</b> is integrally formed at the base of a rotary brake shaft <b>129</b> and the movable friction pad <b>130</b> has a cam projection <b>131</b> projecting from a surface not facing brake rotor. A sleeve <b>132</b> is fixed to upper housing part <b>21</b> and has an opening that rotary brake shaft <b>129</b> extends through. A V-shaped groove <b>133</b> is formed at the end of rotary brake shaft <b>129</b> where sleeve <b>132</b> is located and engages with cam projection <b>131</b>. The other end of rotary brake shaft <b>129</b> not adjacent movable friction pad <b>130</b> has a brake arm <b>29</b> mounted thereon that extends perpendicular to rotary brake shaft <b>129</b> and a return spring <b>134</b> surrounding rotary brake shaft <b>129</b> such that brake arm <b>29</b> is located between return spring <b>134</b> and sleeve <b>132</b>.

When brake pedal <b>18</b> is depressed, brake arm <b>29</b> is actuated to rotate rotary brake shaft <b>129</b>, movement of cam projection <b>131</b> presses V-shaped groove <b>133</b> causing movable friction pad <b>130</b> to move towards fixed friction pad <b>128</b>. This movement causes brake rotor <b>121</b> to be clamped between movable friction pad <b>130</b> and fixed friction pad <b>128</b>, stopping movement of brake rotor <b>121</b> and in turn first counter shaft <b>120</b>, thereby resulting in a braking of the gear train. Return spring <b>134</b> facilitates quick release of the braking action and movement of spring <b>134</b> is limited by limiter pin <b>135</b>. The illustrated braking mechanism is merely illustrative of one suitable braking mechanism and other suitable braking mechanisms can be utilized if desired.

As best seen in <figref idrefs="DRAWINGS">FIG. 6</figref>, one end of pump <b>50</b> is mounted on pump mounting surface <b>70</b> of center section <b>67</b> via a valve plate <b>53</b> that has a pair of openings for communication with kidney ports <b>71</b><i>a </i>and <b>71</b><i>b</i>. Pump <b>50</b> includes a cylinder block <b>52</b> rotatably disposed on valve plate <b>53</b>. Pistons are fitted into a plurality of cylindrical bores of cylinder block <b>52</b>. The other end of pump <b>50</b> has a movable swash plate <b>54</b>, which may be a cradle-type swash plate. Above movable swash plate <b>54</b> is an arcuate guide <b>25</b> for movable swash plate <b>54</b>. Movable swash plate <b>54</b> is provided for selectively varying the displacement of hydraulic pump <b>50</b>. A pump input shaft <b>51</b> extends longitudinally through cylinder block <b>52</b> and is perpendicular to axle shaft <b>9</b>L. It will be recognized by those skilled in the art that rotation of pump shaft <b>51</b> serves to drive hydraulic pump <b>52</b>. Pump shaft <b>51</b> engages with a spline bore provided on the rotational axis of cylinder block <b>52</b> such that cylinder block <b>52</b> rotates with pump shaft <b>51</b>.

As best seen in <figref idrefs="DRAWINGS">FIGS. 8 and 21</figref>, a connecting arm <b>55</b> is attached to movable swash plate <b>54</b> at a first end and extends downward therefrom. A first end of a control shaft <b>58</b> extends from a second end of connecting arm <b>55</b> and a second end of control shaft <b>58</b> has a speed control arm <b>28</b> disposed thereon. Speed control arm <b>28</b> has a slot <b>56</b> through which a stopper <b>57</b> goes through and attaches to housing <b>21</b>. Speed control arm <b>28</b> is mechanically connected to control lever <b>17</b>L with one or more rod links or wire cables, such that when control lever <b>17</b>L is moved forward or backward, speed control arm <b>28</b> moves forward or backward. Movement of speed control arm <b>28</b> is translated through control shaft <b>58</b> to connecting arm <b>55</b> and then to movable swash plate <b>54</b>. Movement of swash plate <b>54</b> changes the direction cylinder block <b>52</b> rotates and thereby switches the transaxle assembly between forward movement, neutral, and reverse movement. When stopper <b>57</b> contacts the end of slot <b>56</b>, it limits the movement of speed control arm <b>28</b>.

As best seen in <figref idrefs="DRAWINGS">FIG. 24</figref>, one end of pump shaft <b>51</b> extends from upper housing <b>21</b> and through a stop ring <b>146</b> and then a spline collar <b>142</b>, both of which surround pump shaft <b>51</b>. A bearing support part <b>143</b> that may be cup shaped surrounds spline collar <b>142</b> and extends downward to cover the opening in upper housing <b>21</b> through which pump shaft <b>51</b> extends. Bearing support part <b>143</b> is separated from upper housing through a bearing <b>145</b> having a seal. Input pulley <b>6</b>L is disposed on an outside of bearing support part <b>143</b> such that a rotary part <b>144</b> of input pulley <b>6</b>L faces bearing support part <b>143</b>. This configuration of disposing input pulley <b>6</b>L accommodates for the low positioning of engine <b>2</b>. It is noted that this configuration may also be utilized in an axle driving apparatus other than for driving zero turn radius vehicles.

<figref idrefs="DRAWINGS">FIG. 24</figref> illustrates a first embodiment for disposing cooling fan <b>7</b>L having fan blades <b>148</b> and a main body <b>149</b> about pump shaft <b>51</b>. Main body <b>149</b> of cooling fan <b>7</b>L is disposed about spline collar <b>142</b> and is attached to bearing support part <b>143</b> through bolts <b>150</b>. In this first embodiment the end of pump shaft <b>51</b> extending through spline collar <b>142</b> has a nut <b>147</b> applied thereto. The rotation of pump shaft <b>51</b> rotates spline collar <b>142</b>, bearing support part <b>143</b> with an outer ring of bearing <b>145</b>, input pulley <b>6</b>L, and cooling fan <b>7</b>L.

<figref idrefs="DRAWINGS">FIG. 25</figref> illustrates a second embodiment for disposing cooling fan <b>7</b>L having fan blades <b>148</b> and a main body <b>149</b> about pump shaft <b>51</b>. Spline collar <b>142</b> rests on a first stop ring <b>154</b> and a wave washer <b>153</b> surrounding pump shaft <b>51</b> rests on top of spline collar <b>142</b>. A spline hub <b>152</b> surrounds pump shaft <b>51</b> and is disposed on top of wave washer <b>153</b>. A main body <b>149</b> of cooling fan <b>7</b>L interlocks with spline hub <b>152</b> and a portion also rests on wave washer <b>153</b>. Wave washer <b>153</b> may be a flexible metal and has the advantage of reducing noise between cooling fan <b>7</b>L and input pulley <b>6</b>L. A spacer <b>156</b> surrounds pump shaft <b>51</b> and is disposed on top of spline hub <b>152</b> and a second stop ring <b>155</b> surrounds pump shaft <b>51</b> and is disposed on top of spacer <b>156</b>. The rotation of pump shaft <b>51</b> rotates spline collar <b>142</b>, bearing support part <b>143</b>, and input pulley <b>6</b>L and also rotates spline hub <b>152</b> and cooling fan <b>7</b>L.

The hydraulic circuit for fluid flow between pump <b>50</b> and motor <b>60</b> will be described with reference to FIGS. <b>4</b> and <b>14</b>-<b>20</b>. Pump mounting surface <b>70</b> on center section <b>67</b> has a pair of kidney-shaped ports <b>71</b><i>a </i>and <b>71</b><i>b </i>to take in or discharge oil in cylinder block <b>52</b> of pump <b>50</b> and a leak oil drain groove <b>72</b>. Motor mounting surface <b>73</b> on center section <b>67</b> has a pair of kidney-shaped ports <b>74</b><i>a </i>and <b>74</b><i>b </i>to take in or discharge oil in cylinder block <b>62</b> of motor <b>60</b> and a leak oil drain groove <b>75</b>. In order to establish fluid communication between port <b>71</b><i>a </i>and port <b>74</b><i>a </i>a tilt oil passage <b>77</b><i>a </i>is provided in center section <b>67</b> that connects port <b>71</b><i>a </i>to a first oil passage <b>76</b> in center section <b>67</b>. Port <b>74</b><i>a </i>is also connected to first oil passage <b>76</b>. Tilt oil passage <b>77</b><i>a </i>has an end that opens to the surface of center section <b>67</b> but is provided with a lid <b>77</b><i>b </i>to close the end. In order to establish fluid communication between port <b>71</b><i>b </i>and <b>74</b><i>b </i>a second oil passage <b>78</b> is provided in center section <b>67</b>, which connects ports <b>71</b><i>b </i>and <b>74</b><i>b</i>. First oil passage <b>76</b> has a first charge check valve <b>79</b><i>a </i>and second oil passage <b>78</b> has a second charge check valve <b>79</b><i>b</i>. Stopper ribs <b>81</b>U and <b>81</b>L are disposed within housing <b>20</b> adjacent charge check valves <b>79</b><i>b </i>and <b>79</b><i>a</i>, respectively, as shown in <figref idrefs="DRAWINGS">FIGS. 6</figref>, <b>10</b>, and <b>11</b>. The end surfaces of the charge check valves <b>79</b><i>b </i>and <b>79</b><i>a </i>contact each stopper ribs <b>81</b>U and <b>81</b>L so that charge check valves <b>79</b><i>b </i>and <b>79</b><i>a </i>never fall out from center section <b>67</b>. Accordingly, a closed hydraulic circuit is defined to circulate the operating oil between hydraulic pump <b>50</b> and hydraulic motor <b>60</b>.

Operation of pump <b>50</b> causes one of first oil passage <b>76</b> or second oil passage <b>78</b> to be under high pressure. When first oil passage <b>76</b> is under high pressure first charge check valve <b>79</b><i>a </i>is also under high pressure and its outlet is closed by its ball valve. Similarly, when second oil passage <b>78</b> is under high pressure second charge check valve <b>79</b><i>b </i>is also under high pressure and its outlet is closed by its ball valve. When one of first and second charge check valves <b>79</b><i>a </i>or <b>79</b><i>b </i>is under high pressure the other of first and second charge check valves <b>79</b><i>a </i>or <b>79</b><i>b </i>is under low pressure and the inlet and outlet are connected and replenished with oil. Second charge check valve <b>79</b><i>b</i>, located in second oil passage <b>78</b>, is under high pressure when vehicle <b>1</b> is traveling in reverse. Second charge check valve <b>79</b><i>b </i>has an orifice <b>80</b> that bypasses the inlet and outlet and thereby broadens the area of the neutral band of pump <b>50</b>.

As best seen in <figref idrefs="DRAWINGS">FIG. 9</figref>, one end of each of first oil passage <b>76</b> and second oil passage <b>78</b> lead to drain ports <b>85</b><i>a </i>and <b>85</b><i>b</i>, respectively. Drain ports <b>85</b><i>a </i>and <b>85</b><i>b </i>run parallel to each other and are connected via a shaft hole <b>86</b> that runs perpendicular to and intersects both drain ports <b>85</b><i>a </i>and <b>85</b><i>b</i>. A rotary bypass valve including a rotary bypass shaft <b>87</b> is disposed within shaft hole <b>86</b>. Rotary bypass shaft has oil holes <b>88</b><i>a </i>and <b>88</b><i>b</i>, which are positioned to align with drain ports <b>85</b><i>a </i>and <b>85</b><i>b</i>, respectively. Rotary bypass shaft <b>87</b> extends from center section <b>67</b> and from upper housing <b>21</b> and has a bypass arm <b>30</b> attached to its end.

The rotary bypass valve is switchably operated between a shutoff position and a communication position by rotating rotary bypass shaft <b>87</b> ninety degrees with bypass arm <b>30</b> about the axis of rotary bypass shaft <b>87</b>. In the shutoff position, oil holes <b>88</b><i>a </i>and <b>88</b><i>b </i>are not in communication with drain ports <b>85</b><i>a </i>and <b>85</b><i>b</i>. In the communication position oil holes <b>88</b><i>a </i>and <b>88</b><i>b </i>are in communication with drain ports <b>85</b><i>a </i>and <b>85</b><i>b</i>. Therefore when the transaxle <b>8</b>L is in traction, it is easy to keep the axle shaft <b>9</b>L free-wheeling by operating bypass arm <b>30</b>.

Center section <b>67</b> also has a charge pump case mounting surface <b>82</b> opposite to pump mounting surface <b>70</b> for mounting a hydraulic PTO unit having a charge pump <b>90</b>. Charge pump case mounting surface <b>82</b> has a charge port <b>83</b> that leads to a passage connected to an inlet of first and second charge check valves <b>79</b><i>a </i>and <b>79</b><i>b </i>and an oil groove <b>84</b>.

Charge pump <b>90</b>, as shown in <figref idrefs="DRAWINGS">FIGS. 6</figref>, <b>8</b>, <b>11</b>, and <b>12</b> is a pump which is contained in a charge pump casing <b>91</b> attached to charge pump case mounting surface <b>82</b> of center section <b>67</b> through bolts <b>92</b>. Pump shaft <b>51</b> extends through charge pump casing <b>92</b> and drives charge pump <b>90</b>. Charge pump <b>90</b> is in fluid communication with first and second oil passages <b>76</b> and <b>78</b> through first and second charge check valves <b>79</b><i>a </i>and <b>79</b><i>b </i>and charge port <b>83</b>.

Charge pump <b>90</b> has an inner rotor <b>93</b> disposed about pump shaft <b>51</b> and has a joint pin <b>94</b> that extends through an opening in pump shaft <b>51</b> and is attached at its ends to inner rotor <b>93</b>. An outer rotor <b>95</b> is disposed about inner rotor <b>93</b>. Oil groove <b>84</b> in center section <b>67</b> is aligned with an oil groove <b>98</b> in charge pump casing <b>91</b>. Oil groove <b>98</b> has an oil hole <b>99</b> that leads to an inlet auxiliary port <b>107</b>. Oil groove <b>98</b> also has an oil hole <b>101</b> that drains oil when an implement relief valve <b>100</b> adjusts the pressure of discharge port <b>97</b>. Discharge port <b>97</b> of charge pump <b>90</b> is in communication with outlet auxiliary port <b>106</b>. Oil groove <b>98</b> also has an oil hole <b>103</b>. The oil flowing over oil groove <b>98</b> goes through oil hole <b>103</b> to charge relief valve <b>102</b>. The oil discharged from charge relief valve <b>102</b> goes through drain hole <b>104</b> then flows down to an oil sump <b>34</b> at the bottom of charge pump casing <b>91</b>. Charge pump <b>90</b> also has a suction port <b>96</b> that leads to oil sump <b>34</b>. Oil groove <b>98</b> also has a suction valve <b>105</b> that is in communication with suction port <b>96</b>. Suction valve <b>105</b> may act as a third check valve that prevents free-wheeling when vehicle <b>1</b> stops and comes to a halt.

As shown in <figref idrefs="DRAWINGS">FIG. 4</figref>, both transaxle <b>8</b>L and <b>8</b>R have charge pumps <b>90</b> with auxiliary ports <b>106</b> and <b>107</b>. In transaxle <b>8</b>L the auxiliary ports are open and connected to a hydraulic actuator <b>108</b> and in transaxle <b>8</b>R the auxiliary ports are open and connected to a hydraulic actuator <b>109</b>. Alternatively, transaxle <b>8</b>R may have auxiliary ports that are closed off via a bypass conduit <b>158</b>, as shown in <figref idrefs="DRAWINGS">FIG. 26</figref> or transaxle <b>8</b>R may not have auxiliary ports at all, as shown in <figref idrefs="DRAWINGS">FIG. 27</figref>. Transaxle <b>8</b>R shown in <figref idrefs="DRAWINGS">FIGS. 26</figref> is the same as transaxle <b>8</b>L except for the presence of bypass conduit <b>58</b> and absence of a hydraulic actuator and transaxle <b>8</b>R shown in <figref idrefs="DRAWINGS">FIG. 27</figref> is the same as transaxle <b>8</b>L except for the absence of auxiliary ports <b>106</b>, <b>107</b> and a hydraulic actuator. Hydraulic actuator <b>108</b> for use as hydraulic equipment adjunct to working vehicle such as lift apparatus for mower.

Charge pump <b>90</b> serves to draw lubricating oil in oil sump <b>34</b> into charge pump <b>90</b> and ultimately into first and second oil passages <b>76</b> and <b>78</b> through first and second charge check valves <b>79</b><i>a </i>and <b>79</b><i>b</i>. As shown in <figref idrefs="DRAWINGS">FIG. 6</figref>, a detachable oil filter <b>36</b> is inserted into rear side opening <b>37</b> in housing <b>20</b>. Once oil filter <b>36</b> is inserted into opening <b>37</b>, opening <b>37</b> is sealed with lid <b>38</b>. Oil filer <b>36</b> is in communication with suction valve <b>105</b> and suction port <b>96</b> of charge pump <b>90</b>.

Alternatively, as shown in <figref idrefs="DRAWINGS">FIG. 28</figref>, a detachable annular oil filter <b>162</b> is inserted in a bottom side opening <b>164</b> of housing <b>20</b>. Once oil filter <b>162</b> is inserted into opening <b>164</b>, opening <b>164</b> is sealed with lid <b>165</b>. Charge pump case <b>161</b> is attached to center section <b>159</b> with a sliding guide pin <b>160</b>. A spring <b>163</b> located between floating charge pump casing <b>161</b> and lid <b>165</b> and flexibly supports charge pump case <b>161</b> so it is floating within oil filter <b>162</b> on spring <b>163</b>. Charge pump case <b>161</b> and spring <b>163</b> have a similar function as the charge relief valve <b>102</b> as set forth above.

Housing <b>20</b> has an oil sump <b>34</b> located therein and the hydraulic stepless speed change assembly is at least partially immersed in oil sump <b>34</b>. Oil sump <b>34</b> is filled with oil for lubricating and operating the HST. As best seen in <figref idrefs="DRAWINGS">FIG. 7</figref>, reserve oil tank <b>111</b> may be disposed in a holder <b>116</b>, which is attached to an outside surface of upper housing <b>21</b>. Reserve tank <b>111</b> is filled with oil having a normal level <b>113</b> and has a cap <b>114</b> having a breather that communicates the interior of reserve tank <b>111</b> with the atmosphere. A fine tube or siphon <b>112</b> extends from a connector <b>115</b> into the oil in reserve tank <b>111</b>. Connector <b>115</b> is attached to reserve tank <b>111</b> and is in communication with oil sump <b>34</b> through a vertical oil bore formed in upper housing <b>21</b>. Siphon <b>112</b> allows for oil to flow between sump <b>34</b> and reserve tank <b>111</b>.

As the volume of oil in oil sump <b>34</b> increases as the temperature of the oil increases during operation of the HST, the increased volume of oil is directed into reserve tank <b>111</b> through connector <b>115</b> and siphon <b>112</b>. In addition, as the volume of oil in oil sump <b>34</b> decreases as the temperature of the oil decreases, the oil returns to oil sump <b>34</b> from reserve tank <b>111</b> through siphon <b>112</b> and connector <b>115</b>.

As discussed above, housing <b>20</b> has a first chamber <b>31</b> housing a gear train, a second chamber <b>34</b> serving as an oil sump, and a third chamber <b>39</b>, which is an opening located between first chamber <b>31</b> and second chamber <b>34</b>. As best seen in <figref idrefs="DRAWINGS">FIGS. 5 and 13</figref>, the housing <b>20</b> utilizes a magnetic oil-cleaning assembly for cleaning the oil therein by removing metal shavings, generated through the chafing of the gears. First chamber <b>31</b> has a first magnet <b>32</b> preferably located near bull gear <b>125</b>. Second chamber <b>34</b> has a second magnet <b>35</b> preferably located near oil filter <b>36</b>. Third chamber <b>39</b> has a communicating bore <b>43</b> to first chamber <b>31</b> and a communicating bore <b>44</b> to second chamber <b>34</b> and a lid <b>41</b>. Oil passes between first chamber <b>31</b> and second chamber <b>34</b> through third chamber <b>39</b>. Third chamber <b>39</b> is an opening between first chamber <b>31</b> and second chamber <b>34</b> and has a third magnet <b>40</b> that sits in a seat plate <b>42</b>.

The axle driving apparatus disclosed above is advantageous for use in a zero turn radius vehicle, but is not limited to such. It allows a lawn or garden tractor, or other vehicle, with the axle driving apparatus disposed therein to make zero radius turns and facilitates mowing close to trees or other obstacles.

While preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention to such disclosure, but rather it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.